LTTPRs operating modes are defined by the DisplayPort standard and the
generic framework now provides a helper to switch between them, which
is handling the explicit disabling of non-transparent mode and its
disable->enable sequence mentioned in the DP Standard v2.0 section
3.6.6.1.

So use the new drm generic helper instead as it makes the code a bit
cleaner. Since the driver specific implementation holds the
lttrp_common_caps, if the call to the drm generic helper fails, the
lttrp_common_caps need to be updated as the helper has already rolled
back to transparent mode.

Acked-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
---
 .../gpu/drm/i915/display/intel_dp_link_training.c  | 24 +++++-----------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
index 8b1977cfec503c70f07af716ee2c00e7605c6adf..c5bad311edf7b9a5cebb633b9e9692bae397f9ed 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
@@ -119,9 +119,6 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp *intel_dp, bool enable)
 	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
 			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
 
-	if (drm_dp_dpcd_write(&intel_dp->aux, DP_PHY_REPEATER_MODE, &val, 1) != 1)
-		return false;
-
 	intel_dp->lttpr_common_caps[DP_PHY_REPEATER_MODE -
 				    DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV] = val;
 
@@ -146,6 +143,7 @@ static bool intel_dp_lttpr_transparent_mode_enabled(struct intel_dp *intel_dp)
 static int intel_dp_init_lttpr_phys(struct intel_dp *intel_dp, const u8 dpcd[DP_RECEIVER_CAP_SIZE])
 {
 	int lttpr_count;
+	int ret;
 
 	if (!intel_dp_read_lttpr_common_caps(intel_dp, dpcd))
 		return 0;
@@ -172,22 +170,8 @@ static int intel_dp_init_lttpr_phys(struct intel_dp *intel_dp, const u8 dpcd[DP_
 		return lttpr_count;
 	}
 
-	/*
-	 * See DP Standard v2.0 3.6.6.1. about the explicit disabling of
-	 * non-transparent mode and the disable->enable non-transparent mode
-	 * sequence.
-	 */
-	intel_dp_set_lttpr_transparent_mode(intel_dp, true);
-
-	/*
-	 * In case of unsupported number of LTTPRs or failing to switch to
-	 * non-transparent mode fall-back to transparent link training mode,
-	 * still taking into account any LTTPR common lane- rate/count limits.
-	 */
-	if (lttpr_count < 0)
-		goto out_reset_lttpr_count;
-
-	if (!intel_dp_set_lttpr_transparent_mode(intel_dp, false)) {
+	ret = drm_dp_lttpr_init(&intel_dp->aux, lttpr_count);
+	if (ret) {
 		lt_dbg(intel_dp, DP_PHY_DPRX,
 		       "Switching to LTTPR non-transparent LT mode failed, fall-back to transparent mode\n");
 
@@ -196,6 +180,8 @@ static int intel_dp_init_lttpr_phys(struct intel_dp *intel_dp, const u8 dpcd[DP_
 		goto out_reset_lttpr_count;
 	}
 
+	intel_dp_set_lttpr_transparent_mode(intel_dp, false);
+
 	return lttpr_count;
 
 out_reset_lttpr_count:

-- 
2.34.1

> -----Original Message-----
> From: dri-devel <dri-devel-bounces@lists.freedesktop.org> On Behalf Of Abel
> Vesa
> Sent: Monday, February 3, 2025 4:28 PM
> To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>; Maxime Ripard
> <mripard@kernel.org>; Thomas Zimmermann <tzimmermann@suse.de>;
> David Airlie <airlied@gmail.com>; Simona Vetter <simona@ffwll.ch>; Karol
> Herbst <kherbst@redhat.com>; Lyude Paul <lyude@redhat.com>; Danilo
> Krummrich <dakr@redhat.com>; Jani Nikula <jani.nikula@linux.intel.com>;
> Vivi, Rodrigo <rodrigo.vivi@intel.com>; Joonas Lahtinen
> <joonas.lahtinen@linux.intel.com>; Tvrtko Ursulin <tursulin@ursulin.net>;
> Rob Clark <robdclark@gmail.com>; Abhinav Kumar
> <quic_abhinavk@quicinc.com>; Dmitry Baryshkov
> <dmitry.baryshkov@linaro.org>; Sean Paul <sean@poorly.run>; Marijn
> Suijten <marijn.suijten@somainline.org>
> Cc: Bjorn Andersson <andersson@kernel.org>; Konrad Dybcio
> <konradybcio@kernel.org>; Johan Hovold <johan@kernel.org>; dri-
> devel@lists.freedesktop.org; linux-kernel@vger.kernel.org;
> nouveau@lists.freedesktop.org; intel-gfx@lists.freedesktop.org; intel-
> xe@lists.freedesktop.org; linux-arm-msm@vger.kernel.org;
> freedreno@lists.freedesktop.org; Abel Vesa <abel.vesa@linaro.org>; Deak,
> Imre <imre.deak@intel.com>
> Subject: [PATCH v5 3/4] drm/i915/dp: Use the generic helper to control LTTPR
> transparent mode
> 
> LTTPRs operating modes are defined by the DisplayPort standard and the
> generic framework now provides a helper to switch between them, which is
> handling the explicit disabling of non-transparent mode and its
> disable->enable sequence mentioned in the DP Standard v2.0 section
> 3.6.6.1.
> 
> So use the new drm generic helper instead as it makes the code a bit cleaner.
> Since the driver specific implementation holds the lttrp_common_caps, if the
> call to the drm generic helper fails, the lttrp_common_caps need to be
> updated as the helper has already rolled back to transparent mode.
> 
> Acked-by: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Abel Vesa <abel.vesa@linaro.org>

LGTM,
Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com>

> ---
>  .../gpu/drm/i915/display/intel_dp_link_training.c  | 24 +++++-----------------
>  1 file changed, 5 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> index
> 8b1977cfec503c70f07af716ee2c00e7605c6adf..c5bad311edf7b9a5cebb633b9
> e9692bae397f9ed 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c
> @@ -119,9 +119,6 @@ intel_dp_set_lttpr_transparent_mode(struct intel_dp
> *intel_dp, bool enable)
>  	u8 val = enable ? DP_PHY_REPEATER_MODE_TRANSPARENT :
>  			  DP_PHY_REPEATER_MODE_NON_TRANSPARENT;
> 
> -	if (drm_dp_dpcd_write(&intel_dp->aux, DP_PHY_REPEATER_MODE,
> &val, 1) != 1)
> -		return false;
> -
>  	intel_dp->lttpr_common_caps[DP_PHY_REPEATER_MODE -
> 
> DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV] = val;
> 
> @@ -146,6 +143,7 @@ static bool
> intel_dp_lttpr_transparent_mode_enabled(struct intel_dp *intel_dp)  static
> int intel_dp_init_lttpr_phys(struct intel_dp *intel_dp, const u8
> dpcd[DP_RECEIVER_CAP_SIZE])  {
>  	int lttpr_count;
> +	int ret;
> 
>  	if (!intel_dp_read_lttpr_common_caps(intel_dp, dpcd))
>  		return 0;
> @@ -172,22 +170,8 @@ static int intel_dp_init_lttpr_phys(struct intel_dp
> *intel_dp, const u8 dpcd[DP_
>  		return lttpr_count;
>  	}
> 
> -	/*
> -	 * See DP Standard v2.0 3.6.6.1. about the explicit disabling of
> -	 * non-transparent mode and the disable->enable non-transparent
> mode
> -	 * sequence.
> -	 */
> -	intel_dp_set_lttpr_transparent_mode(intel_dp, true);
> -
> -	/*
> -	 * In case of unsupported number of LTTPRs or failing to switch to
> -	 * non-transparent mode fall-back to transparent link training mode,
> -	 * still taking into account any LTTPR common lane- rate/count limits.
> -	 */
> -	if (lttpr_count < 0)
> -		goto out_reset_lttpr_count;
> -
> -	if (!intel_dp_set_lttpr_transparent_mode(intel_dp, false)) {
> +	ret = drm_dp_lttpr_init(&intel_dp->aux, lttpr_count);
> +	if (ret) {
>  		lt_dbg(intel_dp, DP_PHY_DPRX,
>  		       "Switching to LTTPR non-transparent LT mode failed, fall-
> back to transparent mode\n");
> 
> @@ -196,6 +180,8 @@ static int intel_dp_init_lttpr_phys(struct intel_dp
> *intel_dp, const u8 dpcd[DP_
>  		goto out_reset_lttpr_count;
>  	}
> 
> +	intel_dp_set_lttpr_transparent_mode(intel_dp, false);
> +
>  	return lttpr_count;
> 
>  out_reset_lttpr_count:
> 
> --
> 2.34.1